1. The Field of the Invention
The present invention relates generally to a total knee replacement by using a prosthetic knee, and more particularly, providing a more functionally correct motion of the prosthetic knee similar to kinematic motion of a normal, non-prosthetic knee, during knee flexion.
2. The Relevant Technology
One attribute of normal knee flexion is that, as the knee flexes, the contact points of the femur on the tibia move posteriorly. This posterior movement of the contact points is known as rollback. Also, normal knee rollback is much more pronounced on the lateral side of the knee than the medial side, which results in femoral external rotation during knee flexion.
Other prosthetic knees currently on the market do not use two separate fully guided motion paths, and as a consequence may not reproduce normal knee kinematics and need to use wear components made of polyethylene, or similar material, to accommodate the less-guided sliding that occurs during knee flexion. These existing methods and procedures may not be as effective as desired. There is a need to have a tibial insert (also known and synonymously referred throughout the specification and claims herein as a “tibial bearing”, “insert”, “bearing insert”, or “tibial bearing insert”) of a prosthetic knee roll back on a medial pivot axis causing greater rollback on the lateral side than the medial side, like a normal, non-prosthetic knee.